The lavatory unit of the seat type has become more and more popular these days in Japan because it makes the user feel extremely less fatigued and more comfortable as compared with the one of the Japanese type. However, some feel disagreeable, and difficult from their physical deficiencies in this case, when they are to open and close the seating plate and the cover plate of the lavatory unit of the seat type. As a fact, it is not sanitary to open and close the seating plate by hand.
Therefore, various kinds of proposals have been made to open and close the seating plate and the cover plate through electric means, and mechanical means such as the pedal. In the case of using the electric means, some problems are caused on the cost and maintenance. In addition, it is useless when power supply is stopped. In the other case of using the mechanical means such as the pedal, those problems which follow the electrical means are not caused because the pedal operation is mechanically associated with the opening and closing of the seating or cover plate. However, the seating and cover plates must be swung to an angle larger than 90.degree. and the stroke of the pedal operation is thus made large, so that the user cannot feel easy to operate the pedal. It is certainly possible to swing the seating or cover plate to an angle of 90.degree. only by pushing the pedal a little by foot. However, the force which is to be added to the pedal must be large in this case, so that the user cannot feel easy to operate the pedal, too.